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Engine internal spray measurements



 

LaVision provides optical access to a running engine using endoscopes and illumination probes for the camera and lighting.

 

The EngineMaster inspex is a direct upgrade from a SprayMaster inspex to be synchronized and operated on engine test beds.

 

These systems visualize the fuel spray directly inside the engine with mi-nimum modifications.

 


 

digital camera

 

camera endoscope

 

 

light engine illumination unit  
source  
   

 

sealing sleeves

 

engine synchronization unit

 

 

crank angle encoder


Laser Imaging in Sprays

 

Droplet Sizing Systems

 

ParticleMaster Shadow


 

Based on imaging shadow projections of droplets the method of Shadow-graphy is applied in a small volume at a desired position within a spray (local). Quantitative absolute results are obtained and a range of lightsour-ces from pulsed LEDs to lasers can be used as backlight source. A long di-stance microscope assures a safe working distance at a high magnification to even detect very small droplets.

4droplet size and velocity incl. correlations

 

4drop shape (eccentricity)4statistics, histograms (D10, D32, DV50)


 

Raw image Detected droplets Particle size histogram

 

 

ParticleMaster IMI The approach with interferometric Mie Imaging (IMI) is recommendable  
for scarce sprays and uses a laser light sheet thus observing a larger area  
   
  than Shadowgraphy. From defocused imaging in forward scattering direc-  
  tion interference fringe patterns are recorded which contain the informati-  
  on about droplet size in the fringe frequency.  
  4droplet size and velocity  
  4size/velocity correlation  
  4statistics, histograms (D10, D32, DV50)  


 

SprayMaster D32


 

 

Standard circular fringe patterns Compressed fringe patterns  
for denser sprays  

 

 

An instantaneous global droplet size map is obtained from the LIF/Mie technique where simultaneously a fluorescence signal (propotional to dro-plet volume) and a Mie signal (proportional to surface area) are recorded and divided by each other. This gives the Sauter Mean Diameter (SMD, D32) from a single laser pulse (fluorescent tracer required).



 

LIF = volume Mie = surface D32


 

 


 

SprayMaster LIF

 

SprayMaster Exciplex

 

FlowMaster


Laser Imaging

In Sprays

 

 

The Laser Induced Fluorescence (LIF) signal is proportional to the droplet mass and, therefore, contains a different information from what can be observed with purely Mie scattered light, which is proportional to the sur-face of the droplet. In combination with PIV the mass flux can be derived.

 

 

Liquid mass distribution

 

Laser Induced Exciplex Fluorescence (LIEF) allows simultaneous visualiza-tion of the two phases. Due to the special LIF tracers the signals from the liquid and the vapor phase can be spectrally separated by optical filters.

 

 

Liquid phase Vapor phase

 

Velocity field measurements using Particle Image Velocimetry (PIV) are well established in fluid mechanics and can be applied to spray droplets or the surrounding air (with additional seeding). The double-pulse laser of a FlowMaster system is an excellent basis for upgrades to many other techniques.

  et al, 2014,Sci.Technol. 25 095204  
2-phase flow field of spray ZhangMeas.  
droplets and ambient air  
   

 


Laser Imaging

 

In Fuel Sprays


 

 

In-cylinder spray imaging



 

Fuel sprays determine to a large extend the fuel/air mixing process in e. g. IC-engines and gas turbines and, thus, the quality of the combustion process itself. Laser imaging provides useful information about the fuel concentra-tion distribution, evaporation and, finally, maps of fuel/air mixture ratios.

 

 

Nowadays laser imaging is a routinely used measurement tool for the in-vestigation of fuel sprays in high pressure test cells or directly inside the combustion chamber. Keyhole imaging can be realized using laser and camera endoscopes, respectively.

 

Laser spray imaging offers an efficient analytical method for spray charac-terization replacing old “trial and error” approaches and provides useful data for the validation of CFD models.


 

 

    Max
Time Development   Fuel Concentration
    Min
  DI-gasoline injection  
Exciplex   Monomer
Fluorescence t= 1000 µs Fluorescence

 

Liquid phase vapor phase

 

Vaporizing fuel spray

 

liquid fuel vapor fuel -Munich  
Mie PLIF  
    Image courtesy of TU  

 

Jet fuel distribution in a gas turbine combustor


 

 


 


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